Escape Velocity Calculator Knowledge Check

The escape velocity of a black hole is equal to the speed of light ($3 \times 10^8$ m/s). If a giant star with mass $M = 8 \times 10^{30}$ kg collapses, at what radius (in km) does its escape velocity equal the speed of light? (Use $G = 6.67 \times 10^{-11}$)